Conventionally, for example, Japanese Patent Laying-Open No. 7-291626 describes a method of depositing an intermediate layer where an oxide superconducting layer is formed with the intermediate layer interposed on a substrate.
In the technique described in this publication, an intermediate layer is formed by a laser ablation method in which a target material is irradiated with laser light and a substance scattered from the target material is evaporated onto a substrate. A film having a particular crystal axis approximately parallel to the normal line direction to the substrate is formed by depositing the intermediate layer with the substrate inclined at a prescribed angle with respect to the target material .
Therefore, as the intermediate layer formed on the substrate is oriented in a particular direction, a superconducting layer formed thereon is also oriented, resulting in an excellent superconducting characteristic.
In the method described in the aforementioned publication, however, since the substrate is positioned inclined to the target material, the distance between one end of the substrate and the target material is relatively large while the distance between the other end of the substrate and the target material is relatively small. The film thickness of the intermediate layer is reduced on the one end side at a long distance from the target material while the film thickness of the intermediate layer is increased at the other end side at a short distance from the target material. The film thickness of the intermediate layer thus varies greatly.
Generally, the film thickness of the intermediate layer is correlated with the orientation of the intermediate layer. As the film thickness of the intermediate layer is increased, the orientation is improved. Therefore, the variations in film thickness result in variations in orientation. As a result, the superconducting layer formed on the intermediate layer varies in orientation, thereby preventing an excellent superconducting characteristic.
The film thickness of the intermediate layer also affects the surface coarseness of the intermediate layer. As the film thickness of the intermediate layer is increased, the surface coarseness is increased. Since the variations in the film thickness of the intermediate layer result in variations in surface coarseness, the superconducting layer formed thereon varies in orientation. This also prevents an excellent superconducting characteristic.
In addition, since the substrate is inclined to the target material and a source material of the intermediate layer is evaporated only from one direction, a particular crystal orientation of the intermediate layer, which should essentially be parallel to the normal line direction to the substrate, is not parallel with the normal line direction. Formation of a superconducting layer on such an intermediate layer gives an adverse effect on the orientation of the superconducting layer, resulting in a deteriorated superconducting characteristic.